Debian init script support and Monit version bump to 5.8

I've added support for Debian Sysvinit where Ohai returns a platform attribute of "debian". A standard /etc/init.d/monit file will be created, along with a /etc/default/monit file which has variables pre-set to start Monit.

I've also bumped the default Monit version to 5.8 as 5.6 is no longer at the url this cookbook looks for. 

Kitchen tests included :)